In mid-2374, Ma'adeen ordered the Tenth Fleet on training exercises, a course of action that would prove to be disastrous for his fleet and the planet he was tasked with defending, Betazed. Possibly due to overconfidence in the security of his location based on Starfleet Intelligence reports that discounted an attack on the planet and by mild subspace fluctuations that interfered with the fleet's sensors his fleet strayed out of position.
When the Dominion fleet arrived they found the fleet in a mock battle formation due to Ma'adeen's orders and were able to quickly destroy twenty Starfleet vessels. Ma'adeen managed to rally his forces, but it was too late. The Dominion systematically destroyed his fleet one ship at a time and Ma'adeen considered surrender but instead decided on buying the Betazoids as much time as possible to prepare. On his orders the entire fleet, including himself, fought to the last ship in a valiant seven hour last stand to save Betazed. Despite his efforts in under three hours the planet fell to the Dominion. (The Dominion War Sourcebook: The Fires of Armageddon)